/* Copyright (C) 2003-2015 LiveCode Ltd.

This file is part of LiveCode.

LiveCode is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License v3 as published by the Free
Software Foundation.

LiveCode is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with LiveCode.  If not see <http://www.gnu.org/licenses/>.  */

#include "foundation.h"
#include "bsdiff.h"

////////////////////////////////////////////////////////////////////////////////

static bool bsdiffmain(MCBsDiffInputStream *old_stream, MCBsDiffInputStream *new_stream, MCBsDiffOutputStream *patch_stream);

bool MCBsDiffBuild(MCBsDiffInputStream *p_old_stream, MCBsDiffInputStream *p_new_stream, MCBsDiffOutputStream *p_patch_stream)
{
	return bsdiffmain(p_old_stream, p_new_stream, p_patch_stream);
}

////////////////////////////////////////////////////////////////////////////////

/*-
 * Copyright 2003-2005 Colin Percival
 * All rights reserved
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted providing that the following conditions 
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#define MIN(x,y) (((x)<(y)) ? (x) : (y))

typedef uint8_t u_char;

static void split(off_t *I,off_t *V,off_t start,off_t len,off_t h)
{
	off_t i,j,k,x,tmp,jj,kk;

	if(len<16) {
		for(k=start;k<start+len;k+=j) {
			j=1;x=V[I[k]+h];
			for(i=1;k+i<start+len;i++) {
				if(V[I[k+i]+h]<x) {
					x=V[I[k+i]+h];
					j=0;
				};
				if(V[I[k+i]+h]==x) {
					tmp=I[k+j];I[k+j]=I[k+i];I[k+i]=tmp;
					j++;
				};
			};
			for(i=0;i<j;i++) V[I[k+i]]=k+j-1;
			if(j==1) I[k]=-1;
		};
		return;
	};

	x=V[I[start+len/2]+h];
	jj=0;kk=0;
	for(i=start;i<start+len;i++) {
		if(V[I[i]+h]<x) jj++;
		if(V[I[i]+h]==x) kk++;
	};
	jj+=start;kk+=jj;

	i=start;j=0;k=0;
	while(i<jj) {
		if(V[I[i]+h]<x) {
			i++;
		} else if(V[I[i]+h]==x) {
			tmp=I[i];I[i]=I[jj+j];I[jj+j]=tmp;
			j++;
		} else {
			tmp=I[i];I[i]=I[kk+k];I[kk+k]=tmp;
			k++;
		};
	};

	while(jj+j<kk) {
		if(V[I[jj+j]+h]==x) {
			j++;
		} else {
			tmp=I[jj+j];I[jj+j]=I[kk+k];I[kk+k]=tmp;
			k++;
		};
	};

	if(jj>start) split(I,V,start,jj-start,h);

	for(i=0;i<kk-jj;i++) V[I[jj+i]]=kk-1;
	if(jj==kk-1) I[jj]=-1;

	if(start+len>kk) split(I,V,kk,start+len-kk,h);
}

static void qsufsort(off_t *I,off_t *V,u_char *old,off_t oldsize)
{
	off_t buckets[256];
	off_t i,h,len;

	for(i=0;i<256;i++) buckets[i]=0;
	for(i=0;i<oldsize;i++) buckets[old[i]]++;
	for(i=1;i<256;i++) buckets[i]+=buckets[i-1];
	for(i=255;i>0;i--) buckets[i]=buckets[i-1];
	buckets[0]=0;

	for(i=0;i<oldsize;i++) I[++buckets[old[i]]]=i;
	I[0]=oldsize;
	for(i=0;i<oldsize;i++) V[i]=buckets[old[i]];
	V[oldsize]=0;
	for(i=1;i<256;i++) if(buckets[i]==buckets[i-1]+1) I[buckets[i]]=-1;
	I[0]=-1;

	for(h=1;I[0]!=-(oldsize+1);h+=h) {
		len=0;
		for(i=0;i<oldsize+1;) {
			if(I[i]<0) {
				len-=I[i];
				i-=I[i];
			} else {
				if(len) I[i-len]=-len;
				len=V[I[i]]+1-i;
				split(I,V,i,len,h);
				i+=len;
				len=0;
			};
		};
		if(len) I[i-len]=-len;
	};

	for(i=0;i<oldsize+1;i++) I[V[i]]=i;
}

static off_t matchlen(u_char *old,off_t oldsize,u_char *newp,off_t newsize)
{
	off_t i;

	for(i=0;(i<oldsize)&&(i<newsize);i++)
		if(old[i]!=newp[i]) break;

	return i;
}

static off_t search(off_t *I,u_char *old,off_t oldsize,
		u_char *newp,off_t newsize,off_t st,off_t en,off_t *pos)
{
	off_t x,y;

	if(en-st<2) {
		x=matchlen(old+I[st],oldsize-I[st],newp,newsize);
		y=matchlen(old+I[en],oldsize-I[en],newp,newsize);

		if(x>y) {
			*pos=I[st];
			return x;
		} else {
			*pos=I[en];
			return y;
		}
	};

	x=st+(en-st)/2;
	if(MCMemoryCompare(old+I[x],newp,MIN(oldsize-I[x],newsize))<0) {
		return search(I,old,oldsize,newp,newsize,x,en,pos);
	} else {
		return search(I,old,oldsize,newp,newsize,st,x,pos);
	};
}

static void offtout(off_t x,u_char *buf)
{
	off_t y;

	if(x<0) y=-x; else y=x;

		buf[0]=y%256;y-=buf[0];
	y=y/256;buf[1]=y%256;y-=buf[1];
	y=y/256;buf[2]=y%256;y-=buf[2];
	y=y/256;buf[3]=y%256;y-=buf[3];
	y=y/256;buf[4]=y%256;y-=buf[4];
	y=y/256;buf[5]=y%256;y-=buf[5];
	y=y/256;buf[6]=y%256;y-=buf[6];
	y=y/256;buf[7]=y%256;

	if(x<0) buf[7]|=0x80;
}

static bool bsdiffmain(MCBsDiffInputStream *p_old_file, MCBsDiffInputStream *p_new_file, MCBsDiffOutputStream *p_patch_file)
{
	u_char *old,*newp;
	off_t oldsize,newsize;
	off_t *I,*V;
	off_t scan,pos,len;
	off_t lastscan,lastpos,lastoffset;
	off_t oldscore,scsc;
	off_t s,Sf,lenf,Sb,lenb;
	off_t overlap,Ss,lens;
	off_t i;
	off_t dblen,eblen;
	u_char *db,*eb;

	// if(argc!=4) errx(1,"usage: %s oldfile newfile patchfile\n",argv[0]);
	bool t_success;
	t_success = true;
    
    V = NULL;

	/* Allocate oldsize+1 bytes instead of oldsize bytes to ensure
		that we never try to malloc(0) and get a NULL pointer */
	/*if(((fd=open(argv[1],O_RDONLY,0))<0) ||
		((oldsize=lseek(fd,0,SEEK_END))==-1) ||
		((old=malloc(oldsize+1))==NULL) ||
		(lseek(fd,0,SEEK_SET)!=0) ||
		(read(fd,old,oldsize)!=oldsize) ||
		(close(fd)==-1)) err(1,"%s",argv[1]);*/
	if (t_success)
	{
		uint32_t t_size;
		t_success = p_old_file -> Measure(t_size);
		oldsize = (signed)t_size;
	}
	if (t_success)
		t_success = MCMemoryNewArray(oldsize + 1, old);
	if (t_success)
		t_success = p_old_file -> ReadBytes(old, oldsize);
	
	/*if(((I=malloc((oldsize+1)*sizeof(off_t)))==NULL) ||
		((V=malloc((oldsize+1)*sizeof(off_t)))==NULL)) err(1,NULL);*/
	if (t_success)
		t_success = MCMemoryNewArray(oldsize + 1, I);
	if (t_success)
		t_success = MCMemoryNewArray(oldsize + 1, V);

    if (t_success)
        qsufsort(I,V,old,oldsize);

	/*free(V);*/
    MCMemoryDeleteArray(V);

	/* Allocate newsize+1 bytes instead of newsize bytes to ensure
		that we never try to malloc(0) and get a NULL pointer */
	/*if(((fd=open(argv[2],O_RDONLY,0))<0) ||
		((newsize=lseek(fd,0,SEEK_END))==-1) ||
		((newp=malloc(newsize+1))==NULL) ||
		(lseek(fd,0,SEEK_SET)!=0) ||
		(read(fd,newp,newsize)!=newsize) ||
		(close(fd)==-1)) err(1,"%s",argv[2]);*/
	if (t_success)
	{
		uint32_t t_size;
		t_success = p_new_file -> Measure(t_size);
		newsize = (signed)t_size;
	}
	if (t_success)
		t_success = MCMemoryNewArray(newsize + 1, newp);
	if (t_success)
		t_success = p_new_file -> ReadBytes(newp, newsize);

	/*if(((db=malloc(newsize+1))==NULL) ||
		((eb=malloc(newsize+1))==NULL)) err(1,NULL);*/
	if (t_success)
		t_success = MCMemoryNewArray(newsize + 1, db);
	if (t_success)
		t_success = MCMemoryNewArray(newsize + 1, eb);

	dblen=0;
	eblen=0;

	/* Create the patch file */
	/*if ((pf = fopen(argv[3], "w")) == NULL)
		err(1, "%s", argv[3]);*/

	/* Header is
		0	8	 "BSDIFF40"
		8	8	length of bzip2ed ctrl block
		16	8	length of bzip2ed diff block
		24	8	length of new file */
	/* File is
		0	32	Header
		32	??	Bzip2ed ctrl block
		??	??	Bzip2ed diff block
		??	??	Bzip2ed extra block */
	/*memcpy(header,"BSDIFF40",8);
	offtout(0, header + 8);
	offtout(0, header + 16);
	offtout(newsize, header + 24);
	if (fwrite(header, 32, 1, pf) != 1)
		err(1, "fwrite(%s)", argv[3]);*/
	uint32_t t_control_size, t_diff_size, t_extra_size;
	t_control_size = 0;
	t_diff_size = 0;
	t_extra_size = 0;
	if (t_success)
		t_success =
			p_patch_file -> WriteInt32(t_control_size) &&
			p_patch_file -> WriteInt32(t_diff_size) &&
			p_patch_file -> WriteInt32(t_extra_size) &&
			p_patch_file -> WriteInt32(newsize);

	/* Compute the differences, writing ctrl as we go */
	/*if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)
		errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);*/
	scan=0;len=0;
	lastscan=0;lastpos=0;lastoffset=0;
	while(t_success && scan<newsize) {
		oldscore=0;

		for(scsc=scan+=len;scan<newsize;scan++) {
			len=search(I,old,oldsize,newp+scan,newsize-scan,
					0,oldsize,&pos);

			for(;scsc<scan+len;scsc++)
			if((scsc+lastoffset<oldsize) &&
				(old[scsc+lastoffset] == newp[scsc]))
				oldscore++;

			if(((len==oldscore) && (len!=0)) || 
				(len>oldscore+8)) break;

			if((scan+lastoffset<oldsize) &&
				(old[scan+lastoffset] == newp[scan]))
				oldscore--;
		};

		if((len!=oldscore) || (scan==newsize)) {
			s=0;Sf=0;lenf=0;
			for(i=0;(lastscan+i<scan)&&(lastpos+i<oldsize);) {
				if(old[lastpos+i]==newp[lastscan+i]) s++;
				i++;
				if(s*2-i>Sf*2-lenf) { Sf=s; lenf=i; };
			};

			lenb=0;
			if(scan<newsize) {
				s=0;Sb=0;
				for(i=1;(scan>=lastscan+i)&&(pos>=i);i++) {
					if(old[pos-i]==newp[scan-i]) s++;
					if(s*2-i>Sb*2-lenb) { Sb=s; lenb=i; };
				};
			};

			if(lastscan+lenf>scan-lenb) {
				overlap=(lastscan+lenf)-(scan-lenb);
				s=0;Ss=0;lens=0;
				for(i=0;i<overlap;i++) {
					if(newp[lastscan+lenf-overlap+i]==
					   old[lastpos+lenf-overlap+i]) s++;
					if(newp[scan-lenb+i]==
					   old[pos-lenb+i]) s--;
					if(s>Ss) { Ss=s; lens=i+1; };
				};

				lenf+=lens-overlap;
				lenb-=lens;
			};

			for(i=0;i<lenf;i++)
				db[dblen+i]=newp[lastscan+i]-old[lastpos+i];
			for(i=0;i<(scan-lenb)-(lastscan+lenf);i++)
				eb[eblen+i]=newp[lastscan+lenf+i];

			dblen+=lenf;
			eblen+=(scan-lenb)-(lastscan+lenf);

			/*offtout(lenf,buf);
			BZ2_bzWrite(&bz2err, pfbz2, buf, 8);
			if (bz2err != BZ_OK)
				errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);

			offtout((scan-lenb)-(lastscan+lenf),buf);
			BZ2_bzWrite(&bz2err, pfbz2, buf, 8);
			if (bz2err != BZ_OK)
				errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);

			offtout((pos-lenb)-(lastpos+lenf),buf);
			BZ2_bzWrite(&bz2err, pfbz2, buf, 8);
			if (bz2err != BZ_OK)
				errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);*/

			if (t_success)
				t_success =
					p_patch_file -> WriteInt32(lenf) &&
					p_patch_file -> WriteInt32((scan-lenb)-(lastscan+lenf)) &&
					p_patch_file -> WriteInt32((pos-lenb)-(lastpos+lenf));

			if (t_success)
				t_control_size += 12;

			lastscan=scan-lenb;
			lastpos=pos-lenb;
			lastoffset=pos-scan;
		};
	};
	/*BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
	if (bz2err != BZ_OK)
		errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);*/

	/* Compute size of compressed ctrl data */
	/*if ((len = ftello(pf)) == -1)
		err(1, "ftello");
	offtout(len-32, header + 8);*/

	/* Write compressed diff data */
	/*if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)
		errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
	BZ2_bzWrite(&bz2err, pfbz2, db, dblen);
	if (bz2err != BZ_OK)
		errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);
	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
	if (bz2err != BZ_OK)
		errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);*/
	if (t_success)
		t_success = p_patch_file -> WriteBytes(db, dblen);
	if (t_success)
		t_diff_size = dblen;

	/* Compute size of compressed diff data */
	/*if ((newsize = ftello(pf)) == -1)
		err(1, "ftello");
	offtout(newsize - len, header + 16);*/

	/* Write compressed extra data */
	/*if ((pfbz2 = BZ2_bzWriteOpen(&bz2err, pf, 9, 0, 0)) == NULL)
		errx(1, "BZ2_bzWriteOpen, bz2err = %d", bz2err);
	BZ2_bzWrite(&bz2err, pfbz2, eb, eblen);
	if (bz2err != BZ_OK)
		errx(1, "BZ2_bzWrite, bz2err = %d", bz2err);
	BZ2_bzWriteClose(&bz2err, pfbz2, 0, NULL, NULL);
	if (bz2err != BZ_OK)
		errx(1, "BZ2_bzWriteClose, bz2err = %d", bz2err);*/
	if (t_success)
		t_success = p_patch_file -> WriteBytes(eb, eblen);
	if (t_success)
		t_extra_size = eblen;

	/* Seek to the beginning, write the header, and close the file */
	/*if (fseeko(pf, 0, SEEK_SET))
		err(1, "fseeko");
	if (fwrite(header, 32, 1, pf) != 1)
		err(1, "fwrite(%s)", argv[3]);
	if (fclose(pf))
		err(1, "fclose");*/
	if (t_success)
		t_success =
			p_patch_file -> Rewind() &&
			p_patch_file -> WriteInt32(t_control_size) &&
			p_patch_file -> WriteInt32(t_diff_size) &&
			p_patch_file -> WriteInt32(t_extra_size) &&
			p_patch_file -> Rewind();

	/* Free the memory we used */
	/*free(db);
	free(eb);
	free(I);
	free(old);
	free(new);*/
	MCMemoryDeleteArray(db);
	MCMemoryDeleteArray(eb);
	MCMemoryDeleteArray(I);
	MCMemoryDeleteArray(old);
	MCMemoryDeleteArray(newp);

	return t_success;
}
